*{
  margin:0;
  padding:0;
  list-style: none;
}
@w:600px;
@h:400px;
#box{
  width: @w;
  height: @h;
  margin: 30px auto;
  border:1px solid #ccc;
  overflow: hidden;
  position: relative;
  >ul{
    overflow: hidden;
    width:@w*6;
    // position: relative;
    // left:0;
    >li{
      float: left;
      width: @w;
      height: @h;
      font-size: 30px;
      img{
        width: 100%;
        height: 100%;
      }
    }
    
  }
  .btn_box{
    position: absolute;
    z-index:10;
    width: 100%;
    top:50%;
    transform: translateY(-50%);
    >div{
      width: 30px;
      height: 50px;
      background: rgba(0,0,0,0.5);
      line-height: 50px;
      text-align: center;
      color:#fff;
      font-size:20px;
      cursor: pointer;
    }
    .left_btn{
      float: left;
    }
    .right_btn{
      float: right;
    }
  }
}